William Shockley and his teenage son are fishing for freshwater turtles the same way their family has done for four generations in south-central Florida: deploying about a mile of nylon line on four sets of buoys holding 1,000 small hooks baited with bits of bacon in the clear, shallow waters of Lake Grassy.

They're hoping to catch as many as 40 soft-shell turtles on their trot lines - the maximum allowed under a Florida interim rule that took effect last week - to sell to a market in nearby Lakeport. The rule, which allows commercial turtle harvesters to take 20 soft-shells per license per day and recreational fishers to take five per day, was adopted to slow down catches while the Florida Fish and Wildlife Conservation Commission works on a long-term management plan for the state's native amphibians.

Shockley, 39, and son Bryton, 16, said they could live with the restrictions - as long as state wildlife managers take an unbiased look at turtle populations before making the reductions permanent. However, Shockley doesn't believe soft-shells - the species targeted by commercial fishers - are in any peril.

"It would be impossible to over fish the soft-shell turtle population in Florida unless you open all the closed areas," Shockley said. "There are more protected areas for turtles than there are unprotected areas."

Besides closing certain waters, including portions of the St Johns River, to commercial turtle harvest, previous statutes limited the season for soft-shells to nine months. Other species - such as alligator snapping turtles, box turtles, loggerhead musk turtles, Barbour's map turtles, river cooters and diamondback terrapins - already were off limits to commercial harvest.

But a group of turtle scientists from Florida and across the country insist that those restrictions are insufficient to conserve species threatened by insatiable demand from international markets, as well as loss of habitat and natural predation at home.

Members of the International Union for Conservation of Nature/Species Survival Commission are urging the FWC to limit anyone to one freshwater turtle from the wild per day.

"Turtles are not fish. The commission doesn't seem to recognize that," turtle biologist Matt Aresco said. "We know turtles cannot be sustainably harvested. Soft-shells take 10 years to reach maturity. They have totally different life histories and should not be lumped into a commercial fishing license."

Although the FWC issues commercial fishing licenses, it does not have the exact numbers of fishermen who actually catch turtles.

Some fishermen target catfish, for example, but take turtles incidentally. Because the animals live in virtually every river, lake, canal, drainage ditch and retaining pond in the state, estimating their populations is difficult. However, the state keeps track of imports and exports and said less than 10% of freshwater turtles exported from Florida come from the wild; the rest come from about 40 turtle farms across the state.

Aresco counters that the export data is misleading because hatchling turtles raised for the pet trade are combined with larger, wild animals exported for food. China's demand, he said, already has wiped out most of Asia's native turtle populations, so the pressure is on here. Indeed, Lauderhill seafood dealer Wan T Ho confirmed that he sometimes buys as many as 3,000 pounds of live turtles per week, selling some domestically and some overseas.

FWC reptile scientist Bill Turner said he does not believe Florida's turtles are in trouble, but he plans to meet with harvesters, scientists and conservation groups to develop a long-term management plan within the next year.

"My sense of it is we are preventing a problem with these new rules," Turner said. "The rules we passed slowed the harvest to less than it was historically. The real question to me is one of economics. How much interest is there in these turtle populations?" "I think the turtle harvest is dying out. The farms provide most of these. I think the best thing is to consider solutions from the people who know."

Shockley said he is one of those who know. He has lived in Okeechobee his entire life, catching, eating and selling freshwater turtles since he was 8-years-old. He said his best day was a haul of 50 turtles totalling 700 pounds. Shockley, an electrical contractor, doesn't depend on catching turtles to earn a living, and he believes even local commercial fishermen don't, either.

"Maybe 10% of fishermen that are licensed are actually turtle fishing," he said. "Usually, they'll catch a turtle trying to eat the fish on the trot line."

Shockley said the reason he is working to keep the commercial fishery for soft-shells open is for his son. "It gives him an opportunity to make money, and it keeps him out of trouble," Shockley said. "He's not running around trying to be a hoodlum."

The Shockleys didn't exactly strike it rich on Lake Grassy last Friday. After spending about seven hours baiting and rigging the trot lines, another eight hours waiting, then pulling in the lines and burning $100 (£60) in boat and truck fuel, they caught seven soft-shell turtles totalling 110 pounds. The Lakeport dealer paid them $165 (£100). Said Shockley: "Now, that ain't a decent living."